Many products in use today are perishable, at least to a degree, in that their performance may degrade over time when they are exposed to atmospheric air, moisture, or other contamination prior to use. Products which are volatile may have components which evaporate or dissipate, moist products may dry out, and dry products may become damp or soggy.
Containers (or canisters) for these perishable products must have lids and/or closures which ensure the freshness of the products prior to the initial use, even if they are subject to extended periods of storage after manufacture. Such closures must also be able to survive the rigors of transportation and handling, yet be easy to open by the consumer. Particularly when the product involved is a food product, the closure design also preferably includes some tamper-evidency feature to assure the consumer that the product is in its original, edible condition at the time of purchase.
An area of particular interest is the pre-mixed, ready-to-use food product area, especially in the ready-to-use frosting arena. These frosting products are used for icing on cakes and similar baked goods, and are ready to apply to the baked item directly from the container.
With products of this type, one of the main criteria in selecting a suitable container is the ability of the container (particularly in its initial unopened configuration) to resist the migration of moisture out of the product. Moisture loss results in drying out of the product, increasing its viscosity and decreasing its suitability for the intended application. Other products may be more sensitive to migration of gases into or out of the container.
As used herein, the term "hermetic" is intended to refer to seals between container components (namely the lid and container body) which provide at least a degree of resistance to moisture migration out of the container, preferably at least equal to that of the container and lid materials. Such seals may also provide resistance to migration of gases at least equal to that of the container body and lid materials. A seal of such quality would not be detrimental to the performance of the container inasmuch as the performance of the container would be limited by the choice of materials utilized for the lid and container and not by the design of or method of forming the seal employed.
One family of commercially available container designs utilizes a conventional plastic snap-on overcap with a foil inner seal over the mouth of the canister-like package. The inner seal provides a hermetic, tamper-evident initial seal which is protected during shipping by the plastic overcap. Once the inner seal is removed, the plastic overcap can be used to reclose and reseal the container to protect the unused portion of the product until the next use.
These container designs require the use of a double-closure design (inner seal with overcap), thus increasing the quantity of material employed and the additional manufacturing steps to apply both closures sequentially. It is also frequently difficult to bond the foil inner seal to the mouth of the container strongly enough to provide the desired seal properties without making removal of the seal too difficult for consumers. The result is a narrow window of acceptable seal bond strength which balances these competing interests in a consumer-friendly package.
Another family of commercially available container designs utilizes a single closure which is heat-sealed or bonded to the mouth of the container. The closure is then peeled away from the mouth of the container for access to the product, and in a multi-use context the closure is usually insertable into the mouth of the container to provide for a recloseable seal of the container. Visual observation of tamper evidency is often difficult with this type of container design, and frequently the only detectable evidence of tampering is greater-than-normal ease of opening due to the lack of having to peel away the lid.
These container designs rely upon the heat seal or bonded region to provide both the initial hermetic seal and the structural seal to protect the contents during shipping and storage. These container designs still require the balancing of the removal force required to peel the lid free and the strength of the seal for structural purposes. It is possible for rough handling of such a container to subject the heat seal or bonded region to excessive localized stresses which may cause a failure of the hermetic seal, resulting in product spoilage prior to consumer purchase.
Still another family of commercially available container designs utilizes a single closure which is heat-sealed or bonded to the mouth of the container, and which utilizes a weakened area around the closure inboard of the bonded region to provide for severability of the main portion of the closure for access to the product. In a multi-use context, the closure then is insertable into the mouth of the container to provide for a recloseable seal of the container. Tamper evidency is provided by visual observation of the tearing of the weakened area upon opening of the container.
These container designs rely upon the heat seal or bonded region to provide both the initial hermetic seal and the structural seal to protect the contents during shipping and storage. While these designs do not required the heat seal to be of the peelable variety, it is still possible for rough handling of such a container to subject the heat seal or bonded region to excessive localized stresses which may cause a failure of the hermetic seal, resulting in product spoil age prior to consumer purchase.
Yet another family of commercially available container designs employs a mechanical closure system to provide a resealable closure system. These container designs frequently lack the ability to provide for an initial hermetic seal as required for perishable (particularly food) products, and many provide either tamper evidency or recloseability (but few provide both). Many of these container designs are also difficult for the consumer to open due to comparatively higher force requirements to disengage interlocking portions of the container which provide the hermetic initial seal.
Accordingly, it would be desirable to provide a container design which employs a recloseable, resealable closure system with a one-piece lid which provides for an initial hermetic seal with tamper evidence yet has sufficient structural integrity to survive rough treatment during transportation and handling while remaining easy to open.